Air pollution, the contamination of the indoor or outdoor environment by any chemical, physical or biologic agent that modifies the natural characteristics of the atmosphere, has been on a steep rise in numerous cities across the globe. It is one of the primary reasons for deterioration in the quality of urban life and responsible for many deaths and serious health disorders. Pollutants of major public health concern include particulate matter, carbon monoxide, ozone, nitrogen oxide and sulfur dioxide. Motor vehicle emission is a leading cause of air pollution, but difficult to regulate compared to industry emissions, since vehicles move across geographical zones and individual vehicle emissions are not easily estimated. Various government agencies have made (or are considering) attempts to reduce emissions using appropriate incentive mechanisms, for example, tolls or taxes, and/or by publishing area-specific air quality indices to enable environmentally conscious citizens to self-regulate.